The present invention relates generally to a portable computer with mechanism for accumulating mechanical energy for powering the system. It also relates to power supplies for portable electronic equipment and especially to mechanical energy systems able to generate electricity to run low-power portable devices, such as personal computers.
There is a "first generation" computer in a Boston, Mass., computer museum that was made in the 1950's and which fills an entire room with racks, wires, and tubes. The power needed to run the computer is enormous, and the heat generated by the system requires its own air conditioning and cooling system. Second generation computers were designed to use transistors, instead of tubes, and were much smaller, about the size of a large desk, and used much less power. The third generation of computers replaced the discrete transistors with integrated circuits (ICs) and were smaller and used still less power.
Apple Computer, IBM Corporation, and Compaq Computer have popularized the portable computer in recent years. Most models consume enough power to require plugging in to house current, but a few are battery operated. Many so-called "laptop" computers are battery operated, and these typically use LCD display panels instead of CRTs. The glass tube CRTs require a heater current and high voltage second anode potentials, and would drain a battery very quickly. Recent advances in CMOS IC device technology have allowed the production of whole digital systems that can run on fractions of watts. Batteries and the small size of laptop computers allow them to be used literally on the laptop of an airplane passenger while in flight. But there, and other places as well, there is no opportunity to run the computer on house current or to recharge a rundown battery. Spare batteries need to be kept, and replacing them in such situations often proves to be difficult and always disruptive of the work. Recharging a battery also requires a recharger, and these are often awkward and bulky, and therefore are many times left behind.
Alternative energy sources to power portable equipment have existed since before Thomas Edison invented the light bulb and his AC power distribution system to supply the bulbs in homes and businesses. Telephones that sported hand cranks actually contained magnetos that were used to generate a ring current at the other end of the wire to signal that the caller (cranker) wanted attention. Some small engines have magneto ignition systems that eliminate the need for a battery and ignition points. A magnet in the flywheel swings by a pickup coil, and a step-up transformer transforms the current induced to a high voltage that is applied to a spark plug. One-man or two-man hand-crank generators were used during World War II to power emergency radio gear to summon rescue. Batteries could not be relied on in the 1940s to be fresh when the emergency arose. The now old electrical and electronic equipment above used a lot of power, and vigorous cranking was needed just to maintain the output. Thomas Edison also produced a line of hand-cranked phonographs that were purely mechanical. In the United States, these became less popular and were antiquainted by the introduction of commercial 110 VAC electricity to ordinary homes in the 1920s and 1930s.
Watches have recently gone from mechanical to electronic mechanisms and power sources. Wind-up watches with mainsprings have been supplanted by quartz watches that need batteries. The batteries must be replaced every year or two, but that is often preferably to having to remember to wind the watch every day. Self-winding watches have existed as another alternative, and these operate by attaching a weighted pendulum through a ratchet to the mainspring. The weighted pendulum will swing around, as the watch on a user's arm is moved, and wind the mainspring.
Solar power is more and more a practical way of powering electronic devices. Texas Instruments (TI) makes a portable, handheld calculator that has no batteries and runs simply on ambient light. The TI-1795 calculator uses so little power, due to its CMOS circuitry, that a 1 cm by 3 cm solar cell is enough to power the calculator in ordinary office light. (See, U.S. Pat. Nos. 3,819,921; 3,921,142; 3,932,846; 4,115,705; 4,208,720; and 4,348,733.) Even so, a larger system such as a computer, would need a much larger solar panel, and good lighting cannot always be assured.
FIGS. 1A and 1B illustrate typical ways prior art computers have been powered. An AC adaptor supplies input power to a power supply whenever house current (e.g., 110 VAC) is available. This power can be used to both supply a main computer circuit and a battery charger. Whenever AC power is not available, a rechargeable battery takes over and the DC power supply unit regulates the voltage to the main computer circuit. In FIG. 1B, two batteries Mb and Sb, one secondary, are used to give longer battery operation. These batteries may or may not be rechargeable. Secondary battery Sb can be used to ensure uninterrupted operation of the computer during replacement of main battery Mb. A lithium back-up battery BU is commonly used to keep internal clocks going (e.g., calendar and time) and to retain data in memory within main computer circuit CP.
Although batteries give prior art computers and other devices a temporary degree of freedom, eventually the unit must be plugged in and/or the batteries recharged. But if the temporary use exceeds the time the batteries will last, a problem develops, especially if the user is traveling a long distance by plane or train, where ordinary house current is not available. Fresh batteries can be carded along, but the principal advantage of a portable computer would be nullified if many loose pieces have to be carried too. Such computers are not practical for use in jungles, caves, on the high seas, in desert areas, large-scale disaster areas, or other field uses where any reasonable supply of fresh batteries would be exhausted and no opportunity to connect to commercial power exists.